For over thirty-five years it has been possible to replace heart valves, since the advent of the heart-lung machine and various mechanical and tissue heart replacement heart valves designed by surgeons and engineers.
The concept of repairing, rather than replacing, diseased heart valves began with the work of Professor Ake Senning of Zurich in 1960. (Senning A:Fascia lata replacement of aortic valves. J Thorac Cardiovasc Surg 54:465-470 (1967)). Senning used autologous fascia lata to fashion both aortic valve repairs and replacements with a freehand technique, but subsequently abandoned his method by 1970 because of valve failures from thickening and shrinkage of the fresh, untreated tissue.
The concept of valve repair with autologous tissue was resurrected by Professor Alain Carpentier of Paris. Beginning in 1980, he began work with the repair of mitral valve leaflets damaged by rheumatic heart disease, using gusset patches of autologous pericardium treated with a brief immersion in glutaraldehyde. In 1991, Carpentier reported a series of 64 patients who had mitral leaflet augmentation by this technique from 1980 to 1989, with excellent results. (Chauvaud S, Jebara V, Chachques J-C, Asmar BE, Mihaileanu S, Perier P, Dreyfus G, Relland J, Couetil J-P, Carpentier A "Valve extension with glutaraldehyde-preserved autologous pericardium." J Thorac Cardiovasc Surg 102:171-178 (1991)). Importantly, he was able to report that the autologous tissue treated with glutaraldehyde did not thicken or shrink or calcify, up to ten years after implantation for repair. In addition to this method for leaflet augmentation, Carpentier employs a combination of annuloplasty, leaflet resection, and chordal shortening and re-implantation techniques to repair mitral valves.
Duran has used autologous pericardium treated with a brief immersion in glutaraldehyde for repair of diseased aortic valves, with good results, including lack of calcification. (Duran C, Kumar N, Gometza B, Al Halees Z; "Indications and limitations of aortic valve reconstruction." Ann Thorac Surg 52:447-454 (1991)).
A problem with all these approaches, however, is that they were not standardized and thus could not easily be replicated in the limited time available while the patient was on the operating table. As described in U.S. Pat. Nos. 5,326,371; 5,163,955; 5,326,370; and 4,470,157, all of which are incorporated by reference herein as though set forth in full, standardized approaches to valve replacement (in contrast to valve repair) are available. However, such approaches involve the use of a stent.
The problem with a stent-mounted prosthesis is that the stent occupies space, and thereby reduces the effective orifice area of the valve. Another disadvantage is that a stent is foreign material. Prosthetic valve infection is not common, but when it occurs, it is a catastrophic complication. A prosthesis of non-biological material must be replaced, in almost all cases, if it becomes infected.
Bailey pioneered concepts for repair and reconstruction of mitral valves with atrial wall tissue and fascia lata. Carpentier expanded on his concepts with methods for chordal and leaflet repair and annular support of the mitral valve. He first used fully tanned bovine pericardium for this leaflet repairs, but later switched to lightly tanned autologous pericardium because of increasing evidence that the material was durable and resistant to calcific degeneration. More recently, Borowski and his colleagues have reported experimental work with reconstruction concepts that they refer to as remodeling of the mitral valve with lightly tanned autologous pericardium, what they refer to as "a perfect prosthetic material" on the basis of experimental work reported by Love. (Borowski, et al. Ann. Thorac. Surg. 58: 452-57 (1994)) There is a lack of standardization in such repairs, since their technique is essentially free-hand method for leaflet reconstruction without any chordal repair.
Accordingly, it is an object of the invention to provide a method of and apparatus for valve repair which overcomes the disadvantages of the prior art.
The anatomy of the atrioventricular valves (mitral and tricuspid) is different from that of the semilunar cardiac outflow valves (aortic and pulmonic). Whereas the former have irregular geometry with leaflet support provided by annular attachment and chordae tendineae connecting the leaflet free edges to the papillary muscles within the ventricles, the latter have an essentially symmetrical trileaflet geometry with leaflet support provided by the scalloped annular attachment and the fixed length of the leaflet free edges extending from the commissures. With regard to the atrioventricular valves, there is increasing recognition that the chordal apparatus should be maintained for optimal ventricular function, a suggestion first made by Lillehei. (Lillehei, J. Thorac. and Cardiovascular Surg. 47:532-43 (1964)) That means that an ideal prosthetic atrioventricular valve, or any method for repairing or reconstructing an atrioventricular valve, should incorporate or retain the connection of the valve to the papillary muscles of the ventricular wall through the leaflets and chordae tendineae (i.e. retain annulo-papillary continuity). Mechanical valves cannot satisfy this requirement, and bioprosthetic valves are generally stent-mounted, without chordal apparatus. There have been several reports of bioprosthesis designs with chordal mechanisms (tested in the animal laboratory and/or clinically), by, e.g., McPhail; Hofelder; Edwards; Mickleborough; Frater; and, Cox (U.S. Pat. No. 5,480,424). Deac modified the concepts of Hofelder and Edwards, and Mickleborough, to make a stentless mitral valve prosthesis with chordal apparatus (U.S. Pat. No. 5,344,442). The problems with all of the reported methods for mitral valve replacement or reconstruction have been lack of precision and reproducibility, lack of standardized instrumentation to facilitate the valve reconstructions, and lack of suitable material for the reconstructions. There has more recently been a report of mitral replacements, but not repair, with homograft tissue. (Acar, et al., J. Thorac. Cardiovascular Surgery 111(2):367-80 (February, 1996))
Love and colleagues suggested in 1985 that autologous pericardium treated with a brief immersion in dilute glutaraldehyde solution would be a suitable valve repair material. Work by his group, and that of others including Carpentier, Duran and Deac, has shown that autologous pericardium so treated is resistant to calcific degeneration in the juvenile sheep model, and in humans who have undergone valve repair, reconstruction or replacement with that material. Good long term results are being obtained with current generation bovine pericardial bioprostheses in older patients, suggesting that homologous or heterologous repair tissue could be used with that older patient cohort.
There is a need for methodology and surgical instruments for cutting a precisely sized and shaped geometric pattern with which an atrioventricular valve reconstruction can be accomplished, and which will facilitate the reconstruction in a manner that will expedite and standardize the reconstruction. Ideally, the surgical instruments used for the reconstruction are simple, inexpensive, disposable or reusable and available in a full range of sizes.